WO2014176789A1

WO2014176789A1 - Clock recovery method, device and system

Info

Publication number: WO2014176789A1
Application number: PCT/CN2013/075150
Authority: WO
Inventors: 周斌; 王祥
Original assignee: 华为技术有限公司
Priority date: 2013-05-03
Filing date: 2013-05-03
Publication date: 2014-11-06
Also published as: CN104662833A; CN104662833B

Abstract

The present invention relates to the field of communications. Disclosed in an embodiment of the present invention are a clock recovery method, device and system. The method of a central office utilizing an orthogonal sequence to modulate an input signal so as to allow a user end to eliminate far-end crosstalk comprises: the central office respectively generates m DMT signals for each user end, and synchronously transmits the m DMT signals to each user end via n lines connected to n user ends; each line employs one or more pilot tones to transmit the m DMT signals; at least one same pilot tone subset exists in n groups of one or more pilot tones corresponding to the n lines; the coefficients of the pilot tone subsets transmitting the DMT signals on any two lines form an orthogonal matrix, n being greater than or equal to 2, and m being greater than n; and the m DMT signals are used by the user end to acquire the signals consistent with the clock of the central office according to the m DMT signals.

Description

The present invention relates to the field of communications, and in particular, to a clock recovery method, device, and system. Background technique

Digital Subscriber Line (DSL) technology is a high-speed transmission technology for data transmission through Unshielded Twist Pair (UTP), which is copper wire access technology. In terms of investment and operation and maintenance. Compared with fiber access technology, it has obvious advantages.

In theory, DSL can provide uplink and downlink symmetry rates of up to 100 Mbps. However, with the development of various broadband services, customers are increasingly demanding speed. At present, the industry's long-term demand for user rate is likely to reach 400 Mbps from the original 100 Mbps. In order to meet the demand for higher speeds, the ITU-T ITU-T has set up the Gfast project to study the Fiber to the Distribution Point (FTTdp) scenario, using copper wire to provide the final high-speed access. The goal is to provide access rates above 500 Mbps in the 100 m range.

In the traditional DSL technology, due to the long transmission distance and narrow spectrum, the duplex mode of Frequency Division Duplexing (FDD) is generally used to avoid interference between uplink and downlink signals. For the next-generation copper broadband access technology Gfast, due to spectrum expansion (bands up to 250MHz), if the FDD duplex mode is adopted, the design requirements of the analog front end will be very strict. Therefore, ITU-T Q4 has adopted Time Division Duplexing (TDD) as the duplex mode of Gfast. The client of Gfast also needs to track the clock of the central office, so that when the clock between the client and the central office is inconsistent, the user needs clock calibration to obtain a signal consistent with the central office. The inventors have found that the prior art has at least the following problems: In the Gfast system, there is strong far-end interference due to spectrum spreading, so that the signal-to-noise ratio (SNR) of the clock synchronization pilot signal received by the UE is SNR. ) 4 艮 low, which in turn makes the client unable to perform accurate clock calibration. Summary of the invention

Embodiments of the present invention provide a method, a device, and a system for clock recovery. The central office uses an orthogonal sequence to modulate an input signal, so that the user end can eliminate far-end crosstalk, thereby performing accurate The clock is calibrated to obtain a signal that is consistent with the central office clock.

In order to achieve the above objective, the technical solution of the embodiment of the present invention is that, in a first aspect, a clock recovery method is provided, where the method includes:

The central office connected to the n user terminals respectively generates m DMT signals for each user terminal; the central office sends m DMT signals to each user terminal synchronously through n lines connected to the n user terminals. Wherein each of the lines transmits the m DMT signals with one or more pilot tones; the corresponding n groups of the one or more pilot tones on the n lines have at least one identical pilot a subset of the pilot tone subsets on which the DMT signal is transmitted on any two lines constitutes an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n And the user terminal that receives the m DMT signals of the user end acquires a signal consistent with the central office clock according to the m DMT signals. In a first possible implementation manner, according to the first aspect, before the office end sends m DMT signals to each user end synchronously through n lines connected to the n user terminals, the method The method further includes: sending, by the central office, indication information to each user end, where the indication information includes an identification letter of the pilot tone subset that sends the DMT signal, and a preset coefficient, the preset coefficient and each The coefficients on the set of pilot tones that transmit the DMT signal on a line form an orthogonal matrix.

In a second possible implementation manner, combining the first aspect or the first possible implementation manner,

The m is a minimum natural number greater than the n.

In a third possible implementation manner, in combination with the first aspect, the first possible implementation manner, or the second possible implementation manner, the central office is synchronized with the n lines connected to the n user terminals. Sending m DMT signals to each client, including:

The central office sends m DMT signals to each user end synchronously using any n rows of the orthogonal matrix W on the n lines connected to the n user terminals, where the orthogonal matrix W The number of rows is greater than n, and the number of columns of the orthogonal matrix W is equal to m; or,

The central office sends m DMT signals to each user end synchronously using any n columns of the orthogonal matrix W on the n lines connected to the n user terminals, where the orthogonal matrix W The number of columns is greater than n, and the number of rows of the orthogonal matrix W is equal to m.

In a fourth possible implementation manner, the binding third possible implementation manner, a = 2, the orthogonal matrix W is a square matrix of order m _m W, said W "^ 々 recursive form:

1 1

1 -1 where k is a natural number greater than or equal to 1. In a second aspect, a method for clock recovery is provided. The method includes: each client receives m DMT signals sent by a central office, where the m DMT signals are passed by the central office and n user terminals. The connected n lines are synchronously transmitted to each of the UEs; wherein, each line transmits the m DMT signals by using one or more pilot tones; the corresponding n groups of the n lines are the one Or a plurality of pilot tones having at least one identical pilot tone subset; wherein the coefficients on the pilot tone subset of the DMT signal transmitted on any two of the lines form an orthogonal matrix, and the number of the user terminals n is greater than or equal to 2, and the m is greater than the n; each user terminal obtains a signal consistent with the central office clock according to the received m DMT signals. In a first possible implementation, according to the second aspect, before each user end receives the m DMT signals sent by the central office, the method further includes: each user end receiving the indication information sent by the central office The indication information includes an identification letter of the pilot tone subset transmitting the DMT signal, and a preset coefficient, and the preset coefficient and the pilot that sends the DMT signal on each line The coefficients on the subset of sounds form an orthogonal matrix. In a second possible implementation manner, combining the second aspect or the first possible implementation manner,

The m is a minimum natural number greater than the n.

In a third possible implementation, in combination with the second aspect or the first possible implementation manner or the second possible implementation manner, the m DMT signals are used by the central office and the n user terminals Each of the connected n lines is synchronously transmitted to each of the user terminals using any n rows of the orthogonal matrix W, wherein the number of rows of the orthogonal matrix W is greater than n, and the number of columns of the orthogonal matrix W is equal to m ;

Or transmitting, by the central office, m DMT signals to each user end synchronously using any n columns of the orthogonal matrix W on the n lines connected to the n user terminals, wherein the orthogonal The number of columns of the matrix W is greater than n, and the number of rows of the orthogonal matrix W is equal to m.

1 1

1 -1 where k is a natural number greater than or equal to 1. In the fifth possible implementation manner, in combination with the first possible implementation manner, the second possible implementation manner, or the third possible implementation manner, or the fourth possible implementation manner, each of the user terminals respectively And obtaining, according to the _m DMT signals received by each user end, a signal consistent with the central office clock, including: each user terminal according to the m DMT signals received by each user end, and the pre- Setting a coefficient to obtain a phase difference between each user end and the central office; each user terminal performs clock calibration according to the phase difference to obtain a signal consistent with the central office clock.

In a third aspect, a central office is provided, including: a processor, configured to generate m DMT signals for n client terminals connected to the central office respectively;

a transmitter, configured to send, by using n lines connected to the n terminals, m DMT signals to each user end; wherein each line transmits the m pieces by using one or more pilot tones a DMT signal; a corresponding n sets of the one or more pilot tones on the n lines having at least one identical pilot tone subset; wherein the pilots of the DMT signal are transmitted on any two of the lines The coefficients on the subset of the sound constitute an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n; the m DMT signals of the user end are used to receive the m DMT signals. The UE obtains a signal consistent with the central office clock according to the m DMT signals.

In a first possible implementation manner, according to the third aspect, the transmitter is further configured to: before sending, by using, n lines connected to the n user terminals, m DMT signals to each user end Sending indication information to each user end, where the indication information includes identification information of the pilot tone subset of the DMT signal and a preset coefficient, and the preset coefficient and the DMT are sent on each line The coefficients on the set of pilot tones of the signal form an orthogonal matrix.

In a second possible implementation, in combination with the third aspect or the first possible implementation manner,

The m is a minimum natural number greater than the n.

In a third possible implementation, in combination with the third aspect, the first possible implementation manner, or the second possible implementation manner, the transmitter is further configured to: the n pieces connected to the n user ends Each of the n rows of the orthogonal matrix W is used to transmit m DMT signals to each of the UEs, wherein the number of rows of the orthogonal matrix W is greater than n, and the number of columns of the orthogonal matrix W is equal to m. Or for transmitting, in each of the n lines connected to the n user terminals, m DMT signals to each user end using any n columns of the orthogonal matrix W, wherein the orthogonal matrix W The number of columns is greater than n, and the number of rows of the orthogonal matrix W is equal to m.

In a fourth possible implementation manner, in combination with the third possible implementation manner, the orthogonal matrix W is a square matrix W _m of the m-th order, and the W„^々 recursive shape The formula is:

1 1

1 -1 where k is a natural number greater than or equal to 1.

In a fourth aspect, a user terminal is provided, including: a receiver, configured to receive m DMT signals sent by a central office, where the m DMT signals are sent by the central office through n lines connected to n user ends Simultaneously transmitting to each of the UEs; wherein, each of the lines transmits the m DMT signals with one or more pilot tones; corresponding n groups of the one or more pilots on the n lines The sound has at least one identical pilot tone subset; wherein the coefficients on the pilot tone subset of the DMT signal transmitted on any two lines form an orthogonal matrix, and the number n of the user terminals is greater than or equal to 2 , the m is greater than the n;

And a phase-locked loop, configured to acquire, according to the m DMT signals received by the receiver, a signal that is consistent with the central office clock. In a first possible implementation manner, according to the fourth aspect,

The receiver is further configured to: before receiving the m DMT signals sent by the central office, receive the indication information sent by the central office, where the indication information includes an identifier of the pilot tone subset that sends the DMT signal And a predetermined coefficient, wherein the preset coefficient forms an orthogonal matrix with the coefficients on the pilot tone subset of the DMT signal transmitted on each line.

In a second possible implementation manner, in combination with the fourth aspect or the first possible implementation manner,

The m is a minimum natural number greater than the n.

In a third possible implementation manner, in combination with the fourth aspect, the first possible implementation manner, or the second possible implementation manner, the m DMT signals are used by the central office and the n user terminals Any n lines of the orthogonal matrix W are synchronously transmitted to each user end on the connected n lines, wherein The number of rows of the orthogonal matrix W is greater than n, and the number of columns of the orthogonal matrix W is equal to m; or, the orthogonality matrix is respectively used by the central office on the n lines connected to the n user terminals. Any of the n columns of W synchronously transmits m DMT signals to each of the UEs, wherein the number of columns of the orthogonal matrix W is greater than n, and the number of rows of the orthogonal matrix W is equal to m.

In a fourth possible implementation, in combination with the third possible implementation manner, the m= 2 ^k , the orthogonal matrix W is a square matrix W m of the order _m , and the W„^々 recursive form for:

1 1

1 -1 where k is a natural number greater than or equal to 1. In a fifth possible implementation manner, in combination with the first possible implementation manner, the second possible implementation manner, or the third possible implementation manner, or the fourth possible implementation manner, the phase locked loop is further used. In:

Obtaining a phase difference between each user end and the central office according to the m DMT signals received by each user terminal and the preset coefficient; performing clock calibration according to the phase difference, and obtaining the same as the central office clock signal of. A fifth aspect provides a clock recovery system, including a central office and a user end, where the central office is configured to generate m DMT signals for each user end respectively; n lines connected by the UEs synchronously transmit m DMT signals to each client; wherein each line transmits the m DMT signals by using one or more pilot tones; on the n lines Corresponding n sets of the one or more pilot tones have at least one identical pilot tone subset; wherein the coefficients on the pilot tone subset of the DMT signal transmitted on any two lines form an orthogonal matrix The number of the user terminals is greater than or equal to 2, and the m is greater than the n; the m DMT signals of the user end are used by the user end that receives the m DMT signals according to the m DMT signals. Obtain a signal consistent with the central office clock. The user end is configured to: receive m DMT signals sent by the central office, where the m DMT signals are sent by the central office to each user end through n lines connected to the n user terminals; Each of the lines transmits the m DMT signals with one or more pilot tones; corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone subset And a coefficient on the pilot tone subset of the DMT signal on any two of the lines constitutes an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n; each The UE obtains a signal consistent with the central office clock according to the received m DMT signals. The method, device and system for clock recovery provided by the embodiment of the present invention, the central office continuously transmits m DMT signals corresponding to each user end to n user terminals synchronously on the same pilot tone, and any two users The m DMT signals corresponding to the end form an orthogonal matrix, so that each user terminal performs accurate clock calibration according to the _m DMT signals received by the UE to obtain a signal consistent with the central office clock. The prior art has strong remote far-end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the UE is very low, thereby making the user terminal unable to accurately calibrate the clock.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set forth in the description of the claims Other drawings can also be obtained from these drawings on the premise of creative labor. 1 is a schematic structural diagram of a G.fast system according to an embodiment of the present invention;

2 is a schematic structural diagram of a phase locked loop according to an embodiment of the present invention; FIG. 3 is a flowchart of a clock recovery method according to an embodiment of the present invention;

4 is a flowchart of another clock recovery method according to an embodiment of the present invention; FIG. 5 is a flowchart of another clock recovery method according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a central office device according to an embodiment of the present disclosure;

FIG. 7 is a schematic diagram of a user equipment according to an embodiment of the present invention; FIG. 8 is a schematic diagram of another user equipment according to an embodiment of the present invention; FIG. 9 is a schematic diagram of an apparatus applied to a central office side according to an embodiment of the present invention; FIG. 10 is a schematic diagram of an apparatus applied to a user end side according to an embodiment of the present invention. detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

The method for clock recovery provided by the embodiment of the present invention can be applied to any DSL system of Synchronous Time Division Duplexing (STDD) and Synchronous Frequency Division Duplexing (SFDD). The Gfast STDD system is illustrated as an example. Referring to FIG. 1 , a schematic diagram of a Gfast system includes a central office, and the central office can connect n user terminals through n lines connected to n clients, and each line can use one or more pilots. Pilot tone Sends a DMT signal. To ensure that the user end obtains the signal consistent with the central office, the user end needs to be consistent with the clock of the central office. For example, the user end can track the clock of the central office through a phase-locked loop. See FIG. 2, which is a schematic structural diagram of a phase-locked loop. The phase-locked loop includes a phase detector, a loop filter, and a Voltage-Controlled Oscillator (VCO). The signal received by the UE from the central office is used as an input signal of the phase detector. When the clocks of the terminals are inconsistent, the phase-locked loop outputs the phase difference between the user end and the central office through precise phase discrimination, and then obtains a signal consistent with the central office through the loop filtering and the VCO. The embodiments of the present invention are described from the central office side and the user end side respectively, and the cooperation examples of the two are explained at the same time, but this does not mean that the two must be implemented together. In fact, the authority and the user end are separately implemented. At the same time, it also solves the problems existing on the central side and the user side, respectively, but when combined, the better technical effect can be obtained.

See Figure 3 for a schematic diagram of the clock recovery process on the central office side. As shown in the figure, the following steps can be included:

301: The central office connected to the n user terminals respectively generates m DMT signals for each user terminal; 302: The central office sends, to each user end, m DMT signals synchronously through n lines connected to the n user terminals; wherein each line sends the m by using one or more pilot tones The DMT signals; the corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone subset; wherein the guide of the DMT signal is transmitted on any two lines The coefficients on the frequency subset form an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n; the m DMT signals of the user end are used to receive the m DMT signals The user end acquires a signal consistent with the central office clock according to the m DMT signals.

For example, before the office sends the M DMT signals to each of the UEs in synchronization with the n lines connected to the n terminals, the method may further include:

The central office sends the indication information to each user end, where the indication information includes an identification letter of the pilot tone subset that sends the DMT signal, and a preset coefficient, where the preset coefficient is sent on each line. The coefficients on the set of pilot tones of the DMT signal form an orthogonal matrix.

Illustratively, m is the smallest natural number greater than the n. For example, the central office sends m DMT signals to each user end synchronously through n lines connected to the n user terminals, which may include: the central office uses positively on each of the n lines connected to the n user terminals. Having any n rows of the intersection matrix W synchronously transmitting m DMT signals to each of the UEs, wherein the number of rows of the orthogonal matrix W is greater than n, and the number of columns of the orthogonal matrix W is equal to m;

The central office sends m DMT signals to each user end synchronously using any n columns of the orthogonal matrix W on the n lines connected to the n user terminals, wherein the number of columns of the orthogonal matrix W is greater than n, The number of rows of the mating matrix W is equal to m. Illustratively, m = 2 ^k , the orthogonal matrix W is a square matrix W _m of m order, and the recursive form of W _m is:

Where k is a natural number greater than or equal to 1. In the clock recovery method provided by the embodiment of the present invention, the central office sends m DMT signals to each user end synchronously through n lines connected to n user terminals; one or more pilot tones are used for each line. Transmitting m DMT signals; corresponding n sets of one or more pilot tones on the n lines have at least one identical pilot tone subset; and transmitting the pilot tone subset of the DMT signal on any two lines The coefficients form an orthogonal matrix, so that the UE can obtain a signal consistent with the central office clock according to the m DMT signals. The prior art has strong remote far-end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the UE is very low, thereby making the user terminal unable to accurately calibrate the clock. Referring to FIG. 4, a schematic diagram of a clock recovery process on the user side, as shown in the figure, may include the following steps:

401: Each user end receives m DMT signals sent by the central office, and the m DMT signals are sent by the central office to each user end through n lines connected to n user terminals; wherein, each Transmitting, by the one or more pilot tones, the m DMT signals; the corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone subset; The coefficients on the pilot tone subset of the DMT signal on any two of the lines constitute an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n; Before the receiving the m DMT signals sent by the central office, the method further includes: each user end receiving the indication information sent by the central office, where the indication information includes the identifier information of the pilot tone subset of the DMT signal and the preset The coefficient, the preset coefficient and the coefficients on the pilot tone subset of the DMT signal transmitted on each line form an orthogonal matrix.

Illustratively, m is the smallest natural number greater than n.

Exemplarily, each client receives m DMT signals sent by the central office, which may include:

m DMT signals are used by the central office respectively on n lines connected to n user terminals Any n rows of the intersection matrix W are synchronously transmitted to each client, wherein the number of rows of the orthogonal matrix W is greater than n, and the number of columns of the orthogonal matrix W is equal to m;

Between the n lines connected to the n user terminals, the central office uses the n columns of the orthogonal matrix W to transmit m DMT signals to each of the UEs, wherein the number of columns of the orthogonal matrix W is greater than n. The number of rows of the orthogonal matrix W is equal to m. Illustratively, m = l ^k , the orthogonal matrix W is a square matrix W _m of m order, and the recursive form of W _m is:

1 1

w,

1 -1 where k is a natural number greater than or equal to 1.

402: Each user end acquires a signal consistent with the local office clock according to the m DMT signals received by each user terminal.

For example, each user terminal obtains a signal consistent with the central office clock according to the m DMT signals received by each user terminal, and may include:

Each user terminal obtains a phase difference between each user end and the central office according to the m DMT signals received by each user terminal and a preset coefficient; each user terminal performs clock calibration according to the phase difference, and obtains a clock consistent with the central office clock. signal.

A clock recovery method is provided by the embodiment of the present invention. Each user end receives m DMT signals sent by the central office, and m DMT signals are synchronously transmitted to each user by the central office through n lines connected to n user terminals. Transmitting; each line uses one or more pilot tones to transmit m DMT signals; corresponding n sets of one or more pilot tones on the n lines have at least one identical pilot tone subset; and any The coefficients on the pilot tone subset of the DMT signal transmitted on the two lines form an orthogonal matrix, and the UE can perform accurate clock calibration according to the received m DMT signals to obtain a signal consistent with the central office clock. Overcoming the prior art due to spectrum expansion There is a strong remote interference, so that the SNR of the clock synchronization pilot signal received by the UE is very low, which makes the user terminal unable to accurately calibrate the clock. The above method embodiments are described below by way of specific embodiments. See Figure 5, including:

S501: The central office connected to the n clients respectively generates m DMT signals for each user terminal;

S502: The central office sends the indication information to the n clients.

For example, the indication information may include the identifier information of the pilot tone that the UE sends the DMT signal to the UE, so that the UE receives the DMT signal sent by the UE according to the identifier information of the pilot tone, where the pilot tone is The identification information may be the number information of the pilot tones or any other information that can uniquely identify the pilot tones. For example, the indication information may further include a preset coefficient, which may be determined in advance by the central office and the user end, or may be preset by the central office and then sent to the user end. This embodiment does not limit this. For example, the preset coefficient is related to the coefficient of the pilot tone of the DMT signal sent by the central office to the UE. The specific selection method of the preset coefficient will be described in detail in S503 in this embodiment.

S503: the central office sends m DMT signals to each user terminal synchronously through n lines connected to the n user terminals;

Exemplarily, n lines may respectively transmit m DMT signals using one or more pilot tones, and corresponding n groups of one or more pilot tones on the n lines have at least one identical pilot tone subset. For example: When n is 3, let the first line be able to use the pilot tone 1, pilot tone 2, pilot tone 3 to send DMT signal, the second line can use pilot tone 1, lead The tone 5 and the pilot tone 6 transmit the DMT signal, and the third line can transmit the DMT signal by using the pilot tone 1, the pilot tone 4, and the pilot tone 5, and the same pilot tone subset on the above three lines Contains pilot tone 1. Exemplarily, n lines can respectively transmit m DMT signals by using pilot tones in the pilot tone subset, and the coefficients on the pilot tone subsets of the DMT signals transmitted on any two lines form an orthogonal matrix. The number of clients n is greater than or equal to 2, and m is greater than n. The above-mentioned preset coefficients form an orthogonal matrix with the coefficients of the pilot tone subset corresponding to each line. Correspondingly, the coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines may constitute an orthogonal matrix of n*m, and the coefficients and presets of the pilot tone subsets of the m DMT signals corresponding to the n lines The coefficients can form an orthogonal matrix of ( n+1 ) *m. Because the coefficients and preset coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines can form an orthogonal matrix of (n+1)*m, the UE can be based on the m DMTs received by the UE. The coefficients of the signal pilot tone subset and the preset coefficients construct the equation, thereby eliminating crosstalk and accurately phase-detecting. The principle will be described below by taking m equal to 4 and n equal to 3.

In this embodiment, the three user terminals are respectively referred to as the first user end, and the second user end and the third user end are recorded as r when the crosstalk is received. When there is no crosstalk, when the clock between the client and the central office is inconsistent, the model of the four consecutive DMT signals received by the UE is:

When there is crosstalk, when the clock between the client and the central office is inconsistent, the model of the four consecutive DMT signals received by the UE is:

[r _x , r ₂ , r ₃ , r ₄ ] = [yz, yz ² , γζ ³ , γζ ⁴ ] , (ζ = β ^θ ) where y is the signal received when the client and the central office clock are identical, z. The phase difference between the client and the central office when there is no crosstalk. z is the phase difference between the client and the central office when there is crosstalk, when z=z can be solved. , to eliminate crosstalk and achieve accurate phase discrimination.

Exemplarily, the central office synchronizes to send the four DMT signals to the first user end, the second user end, and the third user end respectively. The first user end, the second user end, and the third user in this embodiment are illustrated. The coefficients of the pilot tone subset of the respective four DMT signals of the terminal are not specifically limited, as long as the first user end and the second user end, the second user end and the third user end, and the first user end and the third user are satisfied. The coefficients of the pilot tone subsets of the four DMT signals at the end may constitute an orthogonal matrix, for example, the pilot tone subsets of the four DMT signals of the first user end, the second user end, and the third user end in this embodiment. The coefficients are: 1, -1, 1, and -1; 1, 1, -1, -1; 1, -1, -1, 1. In this embodiment, the preset coefficients are recorded as a1, a2, a3, and a4. It should be noted that, in this embodiment, the selection of the preset coefficient is not specifically limited, as long as the preset coefficient can be satisfied with the first user end. The coefficients of the pilot tone subsets of the four DMT signals of the second user end and the third user end respectively constitute an orthogonal matrix. For example, in this embodiment, al = l, a2 = l, a3 = 1, and a4 = 1, that is, the preset coefficients are 1, 1, 1, and 1. Then, the coefficients and preset coefficients of the pilot tone subset of the four DMT signals of the three UEs can be a\ a2 d 4 1 1 1 1

1 -1 1 -1 I - 1 1 -1

Form the orthogonal matrix W, for example, W is w

1 1 -1 -1 I I - 1 -1

^1⁄2 23 1 -1 -1 1 1 -1 -1 1 The crosstalk model on the user side is y = F(HX + Z), where Y is the signal received when the client and the central office clock are consistent, and X is the local The signal sent by the terminal; Z is the background noise, F is the frequency domain equalization coefficient, and H is the crosstalk coefficient. Since Z is much lower than the crosstalk noise, the Z is slightly ignored in this embodiment, and the crosstalk model before the UEQ side is FEQ (frequency domain equalization) is = H.

Illustratively, 1 of the above coefficients represents transmission X, and -1 represents transmission -x. The four DMT signals sent by the central office to the first user end are respectively x, -x, x, -x;

The four DMT signals sent by the central office to the second user are divided into +, χ, -χ, -χ; the four DMT signals sent by the central office to the third user are χ, -χ, - Hey, hey.

When the client clock and the central office clock are the same, the signals received by the three clients are:

= H*W(2-A,:)x

X

Wherein, J^jj is the four signals continuously received by the first user end when the first user terminal clock and the central office clock are consistent, respectively corresponding to the four DMT signals sent by the central office to the first user end, - χ,χ,-χ; , , ₃ ² , respectively, when the second user terminal is consistent with the central office clock and the central office clock The four received signals respectively correspond to the four DMT signals sent by the central office to the second user, χ, χ, χ, -χ;

, j ₃ ³ , respectively, are four signals continuously received by the third user end when the third client clock and the central office clock are consistent, respectively corresponding to the four DMT signals sent by the central office to the third user terminal, - χ,-χ, X.

Without loss of generality, the first user terminal is taken as an example for description. When the first client clock and the central office clock are inconsistent, the four signals received by the first user end are rL.

r is: ri,^,^ ,^": ^ ² ,^ ²

(1) The following formula is equivalently obtained by (1):

Where z = ie:

Using the orthogonality of the w matrix

In particular, as can be seen from the above formula,

therefore, + =0 a 2

+

a 3

+

a

4

+ y ₄ = yy y ₂ :))' = 0

Oy, y ₄ gets + + + = 0

That is, yl + yl+yl + ( 2 ) is obtained by ( l) ' and ( ² )

That is, lrz ³ + 2r ₂ ^l z ² + 3r ₃ ^l z + 4r ₄ ^l = 0

With (3), solve for _z = z. . Since the crosstalk signal has been eliminated in (2), the accuracy of the z is greatly improved, thereby enabling the user to accurately detect the phase.

According to the above description, when the signal transmitted by the central office satisfies the coefficients of the pilot tone subset of the m DMT signals of any two users, the user terminal can guide according to the m DMT signals received by the UE. The coefficients of the frequency subset and the preset coefficients construct the equation, and the crosstalk can be eliminated by solving the equation for accurate phase discrimination.

Preferably, the central office may also directly send m DMT signals to each user end through n rows connected to n user terminals according to a preset matrix W satisfying the condition on one or more pilot tones. ,

For example, the central office sends m DMT signals to each user end synchronously using any n rows of the orthogonal matrix W on the n lines connected to the n user terminals, wherein the number of rows of the orthogonal matrix W is greater than n. , the number of columns of the orthogonal matrix W is equal to m; or, The central office sends m DMT signals to each user end synchronously using any n columns of the orthogonal matrix W on the n lines connected to the n user terminals, wherein the number of columns of the orthogonal matrix W is greater than n, The number of rows of the mating matrix W is equal to m. Preferably, when = 2, the orthogonal matrix W is a square matrix W _{m of} m order, and the recursive form of W _m is:

twenty two"-'

W

twenty two"

1 1

1 -1 where k is a natural number greater than or equal to 1.

For example, when n is equal to 3, m satisfies m>3, where w = 2, so 2 >", the preferred k takes the smallest integer that satisfies the condition, so = 2, m = 4. The selected matrix ^ is:

1 1 1 1

I - 1 1 -1

Therefore ₄

I I - 1 -1

1 -1 -1 1 Illustratively, the central office can send m DMT signals to n clients according to any of the above rules. This embodiment does not limit this. Specific rules for DMT signals.

For example, for the case of n UEs, the central office transmits m DMT signals on the one or more pilot tones using any n rows other than the first row of the orthogonal matrix ^ according to the following rules, where the first Behavior Preset Coefficient:

1. Align the DMT signals corresponding to the n lines:

2. Fixed constellation point X;

3. Number n clients, starting with 2, followed by 2, 3,

4. The jth client sends a DMT signal according to the jth line of ^, where 1 indicates that X is transmitted, and 1 indicates that -X is transmitted; 5. At the same DMT time, the central office ensures that the same column of ^ is sent.

S504: Each user end acquires a phase difference between each user end and the central office according to the m DMT signals received by each user terminal. For example, the user end may obtain m DMTs received by the user end. The signal and the preset coefficient obtain a phase difference between the user end and the central office;

According to the description in S503, the UE can construct an equation according to the coefficients of the pilot tone subset of the m DMT signals received by the UE and the preset coefficients: a\r _x z ^m - ¹ + a2r ₂ z ^m - ² + dhr^ + · · · + amr _m = 0, so that the phase difference between the client and the central office is obtained.

For example, taking one of the clients as an example, the client can process the received message, I, from the central office according to the following rules to obtain an accurate phase difference:

1. The UE starts receiving the DMT signal from any DMT signal including the above pilot tone;

2. The user end records successive m DMT signals in turn, denoted as r\, r2, r ..., r _m ',

3. The user end constructs an equation according to the received M DMT signals and the preset coefficients sent by the central office. For example, when the preset coefficients sent by the central office are al, a2, a3, am, the equation constructed by the user end is:

+ a2r ₂ z ^m - ² + a3r ₃ z ^m ' ³ + · · · + amr _m = 0;

4. Obtain the phase difference z = z between the user end and the central office from the above structural equation. = ^ ;

5. Use ^ as the output of the phase detector in the phase-locked loop.

S505: Each client performs clock calibration according to the phase difference to obtain a signal consistent with the local clock. Exemplarily, the UE can perform clock calibration according to the output of the phase detector in the phase locked loop to obtain a signal consistent with the central office clock.

For example, in the case of one of the user terminals, the user can perform clock calibration on the information received by the user terminal according to the phase difference obtained by the rule in S504. For example, based on the foregoing S504, the foregoing rules may further include:

6. The phase-locked loop is calibrated according to the clock of the user terminal; obtaining m DMT signals consistent with the central office clock; exemplarily, the user terminal can periodically repeat the above rules 2 to 6 to obtain the relationship A continuous signal with a consistent end clock.

It should be noted that when the number of clients connected by the authority is very large, the central office can be used for the client. After the grouping is performed, the central office sends the DMT signal to each group by using the above method, so that the user terminals in each group can perform accurate clock recovery separately, thereby obtaining a signal consistent with the central office. In the clock recovery method provided by the embodiment of the present invention, the central office sends m DMT signals to each user end synchronously through n lines connected to n user terminals; one or more pilot tones are used for each line. Transmitting m DMT signals; corresponding n sets of one or more pilot tones on the n lines have at least one identical pilot tone subset; and transmitting the pilot tone subset of the DMT signal on any two lines The coefficients form an orthogonal matrix, so that the UE can obtain a signal consistent with the central office clock according to the m DMT signals. The prior art has strong remote far-end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the UE is very low, thereby making the user terminal unable to accurately calibrate the clock.

On the other hand, referring to FIG. 6, a schematic diagram of a device for the central office 60 is provided in the embodiment of the present invention. The central office 60 provided by the embodiment of the present invention can be applied to any Synchronous Time Division Duplexing (STDD). The DSL system of Synchronous Frequency Division Duplexing (SFDD) is used as an example to describe the STDD system of Gfast. Referring to FIG. 1, a schematic diagram of a Gfast system includes a central office 60. The central office 60 can connect n clients through n lines connected to n clients, and each line can use one or more lines. The pilot tone (ilot tone) sends a DMT signal. As shown in Figure 6, the central office 60 includes:

a generating unit 601, configured to generate m DMT signals for n client terminals connected to the central office 60, respectively, and a sending unit 602, configured to synchronize each of the n lines connected to the n user terminals The client sends m DMT signals; wherein, each line transmits the m DMT signals by using one or more pilot tones; corresponding n groups of the one or more pilot tones on the n lines At least one of the same pilot tone subsets; wherein the coefficients on the pilot tone subset of the DMT signal transmitted on any two lines form an orthogonal matrix, and the number n of the user terminals is greater than or equal to 2, The m is greater than the n; the user terminal of the M DMT signals for receiving the m DMT signals acquires a signal consistent with the clock of the central office 60 according to the m DMT signals.

Exemplarily, the sending unit 602 is further configured to: pass through with the n user terminals Before the n lines of the connection are sent to each of the user terminals, the indication information is sent to each of the user terminals, and the indication information may include the identification information of the pilot tone of the DMT signal sent by the central office 60 to the user end. The user terminal receives the DMT signal sent by the central office 60 according to the identification information of the pilot tone. The identification information of the pilot tone may be the number information of the pilot tone or any other information that can uniquely identify the pilot tone.

Exemplarily, the indication information may further include a preset coefficient, which may be determined in advance by the central office 60 and the user end, or may be preset by the central office and then sent to the user end. This embodiment does not limit this.

Exemplarily, the preset coefficient is related to the coefficient of the pilot tone subset of the DMT signal sent by the sending unit 602 to the UE, for example, the coefficient component on the pilot tone subset of the DMT signal transmitted on any two lines. In the orthogonal matrix, the number of clients n is greater than or equal to 2, and m is greater than n. The above-mentioned preset coefficients form an orthogonal matrix with the coefficients of the pilot tone subset corresponding to each line.

Correspondingly, the coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines may constitute an orthogonal matrix of n*m, and the coefficients and presets of the pilot tone subset of the m DMT signals corresponding to the n lines The coefficients can form an orthogonal matrix of ( n+1 ) *m. Because the coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines and the preset coefficients can form an orthogonal matrix of (n+1)*m, the user terminal can be made according to the m received by the UE. The coefficients of the pilot tone subset of the DMT signal and the preset coefficients construct the equation, thereby eliminating crosstalk and accurately phase-detecting. The principle is described below by taking m equal to 4 and n equal to 3.

In this embodiment, the three user terminals are respectively referred to as the first user end, the second user end, and the third user end, and the signal received by the user end when there is crosstalk is recorded as r. When there is no crosstalk, when the clock of the client and the central office 60 are inconsistent, the model of the four consecutive DMT signals received by the UE is:

i , r ₂ , r ₃ , r ₄ ] = [yz ₀ ,

, yz ₀ ⁴ ] , (ζ ₀ = β ^ιθ )

When there is crosstalk, when the clock of the client and the central office 60 are inconsistent, the model of the continuous four DMT signals received by the UE is:

\r _x , r ₂ , r ₃ , r ₄ ] = [yz, yz ² , yz ³ , yz ⁴ ] , (z = e ^l ° ) where y is received when the client and the central office 60 are clocked Signal, z. For no strings The phase difference between the client and the central office 60 at the time of the disturbance. z is the phase difference between the client and the central office 60 when there is crosstalk, when z=z can be solved. , to eliminate crosstalk and achieve accurate phase discrimination.

For example, the central office 60 sends four DMT signals to the first user terminal, the second user terminal, and the third user terminal, respectively, and the first user terminal, the second user terminal, and the third embodiment in this embodiment. The coefficients of the pilot tone subset of the four DMT signals of the user end are not specifically limited, as long as the first user end and the second user end, the second user end and the third user end, and the first user end and the third end are satisfied. The coefficients of the pilot tone subsets of the four DMT signals of the user end may constitute an orthogonal matrix, for example, the pilot tones of the four DMT signals of the first user end, the second user end, and the third user end in this embodiment. The set coefficients are: 1, -1, 1, and -1; 1, 1, -1, -1; 1, -1, -1, 1. In this embodiment, the preset coefficients are recorded as a1, a2, a3, and a4. It should be noted that, in this embodiment, the selection of the preset coefficient is not specifically limited, as long as the preset coefficient can be satisfied with the first user end. The coefficients of the pilot tone subsets of the four DMT signals of the second user end and the third user end respectively constitute an orthogonal matrix. For example, in this embodiment, al = l, a2 = l, a3 = 1, and a4 = l, that is, the preset coefficients are 1, 1, 1, and 1.

Then, the coefficients and preset coefficients of the pilot tone subset of the four DMT signals of the three UEs may constitute an orthogonal matrix W, for example, W

The crosstalk model on the user side is = F(HX + Z), where Y is the signal received when the user end is consistent with the central office 60 clock, X is the signal sent by the central office 60; Z is the background noise, and F is the frequency domain. The equalization coefficient, H is the crosstalk coefficient. Since Z is much lower than the crosstalk noise, the Z is slightly excluded in this embodiment, and the crosstalk model before the UEQ side is FEQ (frequency domain equalization) is = H.

Illustratively, 1 of the above coefficients represents a transmission X, and -1 represents a transmission of -x. Then, the four DMT signals sent by the central office 60 to the first user end are χ, -χ, χ, -χ;

The four DMT signals sent by the central office 60 to the second user end are χ, χ, -χ, -χ;

The four DMT signals sent by the central office 60 to the third UE are χ, -χ, -χ, χ.

When the clock of the client and the clock of the central office are the same, the signals received by the three clients are: = H*W(2-A,:)x

The four signals continuously received by the first user end when the first user terminal clock and the central office clock are the same are respectively corresponding to the four DMT signals sent by the central office 60 to the first user end, respectively. , χ, -χ; , ₂ ² , J ₃ ² , J ₄ ² are respectively 4 signals continuously received by the second user terminal when the second user terminal clock and the central office 60 clock are coincident, respectively corresponding to the central office 60 The four DMT signals χ, χ, -χ, -χ; , jj ₃ ³ , j ₄ ³ sent to the second user end are consecutively received by the third user terminal when the third user terminal clock and the central office 60 clock are coincident. The four signals arriving correspond to the four DMT signals 局, -χ, -χ, χ transmitted by the central office 60 to the third user end.

Without loss of generality, the first user terminal is taken as an example for description. When the clock of the first user terminal and the clock of the central office 60 are inconsistent, the four signals 44^, 4 received by the first user end are: ^, ^ , ^ , ], where ζ = ( 1 ) is equivalently obtained by ( 1 ):

^ΑΐΓ ' I- [ « 4 ]

( 1 )

+

a

2

Using W moments + array orthogonality

a

3

+

a

4

In particular, as can be seen from the above formula,

W(2:4,:)*(W(l,:)) Therefore,

W(2:4,:)*(W(l,:))

+ + + ] = [ ή ή

That is, yl + y2+yl + A=o ( 2) is obtained by (1), and (2)

That is, ΐηζ ³ +

= 0 ie i^ ₊ 4 + 4 + 4 = 0, ie r^ + ^V+r^ + r^O ( 3) With (3), solve for _z = z. . Since the crosstalk signal has been eliminated in (2), the accuracy of the z is greatly improved, thereby enabling the user to accurately detect the phase.

It can be seen from the above description that when the signal transmitted by the central office 60 satisfies the coefficients of the ^2 pilot tone subset of the m DMT signals of any two users, the UE can receive m DMTs received by the UE. The coefficients of the pilot subset of the signal and the preset coefficients construct the equation, which can eliminate the crosstalk for accurate phase discrimination by solving the equation.

Preferably, the central office 60 can also directly send m DMTs to each client by using the matrix W satisfying the condition on one or more pilot tones through n lines connected to the n terminals. Signal,

For example, each of the n lines connected by the central office 60 and the n user terminals respectively transmits m DMT signals to each user end using any n lines of the orthogonal matrix W, wherein the number of rows of the orthogonal matrix W is greater than n. , the number of columns of the orthogonal matrix W is equal to m; or,

The n ends of the orthogonal matrix W are respectively used to transmit m DMT signals to each of the n terminals on the n lines connected to the n user terminals, wherein the number of columns of the orthogonal matrix W is greater than n, The number of rows of the mating matrix W is equal to m. Preferably, when = 2, the orthogonal matrix W is a square matrix W _{m of} m order, and the recursive form of W _m is:

twenty two"

W

twenty two"

1 1

1 -1 where k is a natural number greater than or equal to 1.

For example, when n is equal to 3, m satisfies m>3, where w = 2, so 2 > " , the preferred k takes the smallest integer that satisfies the condition, so = 2 , m = 4. The matrix used ^ is:

1 1

According to ₇

1 -1 1 1 1 1

m ϋ 1 -1 1 -1

So ₄ = .

4 1 1 -1 -1

1 -1 -1 1 Illustratively, the central office 60 can send m DMT signals to n clients according to any of the above rules. This embodiment does not limit this. 60 specific rules for sending DMT signals.

For example, for the case of n clients, the central office 60 transmits m DMT signals on the one or more pilot tones using any n rows other than the first row of the orthogonal matrix ^ according to the following rules, where ^ First behavior preset coefficient:

1. Align the DMT signals corresponding to the n lines;

2. Fixed constellation point X;

3. Number n clients, starting with 2, followed by 2, 3

4. The jth client sends a DMT signal according to the jth line of ^, where 1 indicates that X is transmitted, and -1 indicates that -X is transmitted;

5. At the same DMT time, the central office 60 ensures that the same column of ^ is sent.

It should be noted that when the number of clients connected to the authority 60 is very large, the central office 60 can group the user terminals, and the central office 60 sends the DMT signal to each group by using the above method, so that the user terminals in each group can respectively be separated. Accurate clock recovery is performed to obtain signals that are consistent with the central office 60.

A central office 60 is provided by the embodiment of the present invention. The central office 60 sends m DMT signals to each user end synchronously through n lines connected to n user terminals; one or more pilots are used for each line. The tone transmits m DMT signals; the corresponding n sets of one or more pilot tones on the n lines have at least one identical pilot tone subset; and the pilot tone subset of the DMT signal is transmitted on any two lines The coefficients form an orthogonal matrix, so that the UE can obtain a signal consistent with the clock of the central office 60 according to the m DMT signals. The prior art has strong remote far-end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the UE is very low, thereby making the user terminal unable to accurately calibrate the clock. FIG. 7 is a schematic diagram of an apparatus for a user terminal 70 according to an embodiment of the present invention. The user terminal 70 provided by the embodiment of the present invention can be applied to any Synchronous Time Division Duplexing (STDD), synchronous frequency division. Synchronous Frequency Division Duplexing (SFDD) DSL system, this embodiment The G.fast STDD system is described as an example. Referring to FIG. 1, a schematic diagram of a G.fast system includes a central office, and the central office can connect n client terminals 70 through n lines connected to n client terminals 70, and each line can use one or A plurality of pilot tones transmit a DMT signal. As shown in Figure 7-8, the client 70 can include:

The receiving unit 701 is configured to receive m DMT signals sent by the central office, where the m DMT signals are sent by the central office to each of the user terminals 70 through n lines connected to the n user terminals 70; Transmitting, by each of the lines, the m DMT signals with one or more pilot tones; corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone a set; the coefficients on the pilot tone subset of the DMT signal on any two lines constitute an orthogonal matrix, the number 70 of the user end is greater than or equal to 2, the m is greater than the n; For example, the receiving unit 701 is further configured to: before receiving the m DMT signals sent by the central office, receive the indication information sent by the central office, where the indication information may include the pilot tone that the central office sends the DMT signal to the user end 70. The identifier information is used to receive the DMT signal sent by the central office according to the identification information of the pilot tone. The identifier information of the pilot tone may be the number information of the pilot tone or any other signal that can uniquely identify the pilot tone. information

For example, the indication information may further include a preset coefficient, which may be determined in advance by the central office and the user terminal 70, or may be preset by the central office and then sent to the user terminal 70. This embodiment does not limit this.

Exemplarily, the preset coefficient is related to a coefficient of a pilot tone subset of the DMT signal sent by the central office to the UE 70, for example, a coefficient component on a pilot tone subset of the DMT signal transmitted on any two lines. In the orthogonal matrix, the number of clients n is greater than or equal to 2, and m is greater than n. The preset coefficients described above form an orthogonal matrix with the coefficients of the pilot tone subset corresponding to each line. The preset coefficients and the coefficients of the pilot tone subset of the m DMT signals of each client 70 form an orthogonal matrix. For example, the preset coefficients can be written as al, a2, a3, ..., am.

Correspondingly, the coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines may constitute an orthogonal matrix of n*m, and the coefficients and presets of the pilot tone subset of the m DMT signals corresponding to the n lines The coefficients can form an orthogonal matrix of ( n+1 ) *m.

Illustratively, m is the smallest natural number greater than n. Exemplarily, the m DMT signals are transmitted by the central office to each of the user terminals 70 synchronously using n rows of the orthogonal matrix W on the n lines connected to the n user terminals 70, wherein the orthogonal matrix W The number of rows is greater than n, and the number of columns of the orthogonal matrix W is equal to m;

Alternatively, the central office transmits m DMT signals to each of the user terminals 70 synchronously using any n columns of the orthogonal matrix W on the n lines connected to the n user terminals 70, wherein the columns of the orthogonal matrix W The number is greater than n, and the number of rows of the orthogonal matrix W is equal to m. Illustratively, m = l ^k , the orthogonal matrix W is a square matrix W _m of m order, and the recursive form of W _m is:

1 1

1 -1 where k is a natural number greater than or equal to 1.

The obtaining unit 702 is configured to obtain, according to the m DMT signals received by each user terminal 70, a signal consistent with the central office clock.

Exemplarily, the obtaining unit 702 can include:

The phase difference module 7001 is configured to obtain a phase difference between each user end 70 and the central office according to the m DMT signals received by each user terminal 70 and a preset coefficient. For example, the phase difference module 7001 can receive the receiving unit 701 according to the receiving unit 701. The coefficients of the pilot tone subset of the m DMT signals and the preset coefficients obtain the phase difference between the UE and the central office;

According to the principle description in the method claim S503, when the signal transmitted by the central office satisfies the coefficients of the pilot tone subset of the m DMT signals of any two client terminals 70, the signal received by any user terminal 70 is received. Satisfying a\r _x z ^m - ^x + a2r ₂ z ^m - ² + ir^ + · · · + amr _m = 0, therefore, the phase difference module 7001 can be based on the pilots of the m DMT signals received by the UE 70 The coefficients of the subset and the preset coefficients construct the equation, and the crosstalk can be eliminated by solving the equation for accurate phase discrimination.

For example, the phase difference module 7001 can occupy the coefficients of the pilot tone subset of the m DMT signals received by the UE 70 and the preset coefficient construction equation: a\r _x z ^m - ¹ + air - ¹ + a3rf + ··· + amr _m = 0, thereby obtaining the phase difference between the client terminal 70 and the central office. For example, the client 70 can process the information received from the central office in accordance with the following rules to obtain an accurate phase difference:

1. The UE 70 starts receiving the DMT signal from any DMT signal including the above pilot tone;

2. The client terminal 70 sequentially records successive m DMT signals, which are recorded as rl, r ₂ , r3, ..., r;

3. The user terminal 70 constructs an equation according to the received m DMT signals and the preset coefficients sent by the central office. For example, when the preset coefficients sent by the central office are al, a2, a3, and am, the equation constructed by the user end is: a\rz ^m ' + a2r ₂ z ^m - ² + a3r ₃ z ^m - ³ + · · · + amr _m = 0;

4. The user terminal 70 obtains the phase difference z = z between the client and the central office from the above structural equation. = ^ ;

5. The phase difference module 7001 uses ^ as the output of the phase difference module 7001. The clock calibration module 7002 performs clock calibration according to the phase difference to obtain a signal consistent with the local clock.

Exemplarily, the clock calibration module 7002 can perform clock calibration according to the output of the phase difference module 7001 to obtain a signal consistent with the central office clock.

For example, the clock calibration module 7002 can perform clock calibration on the information received by the client according to the phase difference obtained by the above rules: For example, the foregoing rules may further include:

6. The clock calibration module 7002 calibrates the clock of the user terminal 70 according to ^; obtains m DMT signals consistent with the central office clock; for example, the user terminal 70 can periodically repeat the rules 2 to 6 of the above rule, thereby A continuous signal consistent with the central office clock can be obtained. It should be noted that when there are a large number of client terminals 70 connected by the authority, the central office can group the client terminals 70, and the central office sends the DMT signals to each group by using the above method, so that the user terminals 70 in each group can respectively Perform accurate clock recovery to obtain a signal consistent with the central office.

The user terminal 70 is provided by the embodiment of the present invention. Each user terminal 70 receives m DMT signals sent by the central office, and the m DMT signals are synchronously transmitted by the central office through n lines connected to the n user terminals 70. A user terminal 70 transmits; each line uses one or more pilot tones to transmit m DMT signals; and corresponding n groups of one or more pilot tones on the n lines have at least one identical pilot tone subset And transmit the pilot tone of the DMT signal on any two lines The coefficients on the subset form an orthogonal matrix, and the client 70 can perform accurate clock calibration based on the received m DMT signals to obtain a signal consistent with the central office clock. The prior art has strong remote end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the user terminal 70 is very low, thereby making the user terminal 70 unable to accurately calibrate the clock.

On the other hand, referring to FIG. 9, a schematic diagram of a device for the central office 60 is provided in the embodiment of the present invention. The central office 60 provided by the embodiment of the present invention can be applied to any Synchronous Time Division Duplexing (STDD). The DSL system of Synchronous Frequency Division Duplexing (SFDD) is used as an example to describe the STDD system of Gfast. Referring to FIG. 1, a schematic diagram of a Gfast system includes a central office 60. The central office 60 can connect n clients through n lines connected to n clients, and each line can use one or more lines. The pilot tone (ilot tone) sends a DMT signal. As shown in Figure 9, the central office 60 includes:

The processor 901 is configured to generate m DMT signals for the n clients connected to the central office 60, respectively.

The transmitter 902 is configured to send, by using n lines connected to the n terminals, m DMT signals to each user end, where each line transmits the m by using one or more pilot tones. The DMT signals; the corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone subset; wherein the guide of the DMT signal is transmitted on any two lines The coefficients on the frequency subset form an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n; the m DMT signals of the user end are used to receive the m DMT signals The UE obtains a signal consistent with the clock of the central office 60 according to the m DMT signals.

Exemplarily, the transmitter 902 is further configured to: send, to each user end, indication information before sending, by using, n lines connected to the n user terminals, m DMT signals to each user end, The indication information may include the identifier information of the pilot tone of the DMT signal sent by the central office 60 to the UE, so that the UE receives the DMT signal sent by the central office 60 according to the identification information of the pilot tone, and the identifier information of the pilot tone may be It is the number information of the pilot tone or any other information that can uniquely identify the pilot tone.

Exemplarily, the indication information may further include a preset coefficient, where the preset coefficient may be The terminal 60 and the user end are determined in advance by negotiation, and may be pre-set by the central office according to requirements and then sent to the user end. This embodiment does not limit this.

Exemplarily, the preset coefficient is related to the coefficient of the pilot tone subset of the DMT signal sent by the transmitter 902 to the UE, for example, the coefficients on the pilot tone subset of the DMT signal transmitted on any two lines constitute a positive The mating matrix, the number of clients n is greater than or equal to 2, and m is greater than n. The preset coefficients described above form an orthogonal matrix with the coefficients of the pilot tone subset corresponding to each line.

Correspondingly, the coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines may constitute an orthogonal matrix of n*m, and the coefficients and presets of the pilot tone subset of the m DMT signals corresponding to the n lines The coefficients can form an orthogonal matrix of ( n+1 ) *m. Because the coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines and the preset coefficients can form an orthogonal matrix of (n+1)*m, the user terminal can be made according to the m received by the UE. The coefficients of the DMT signal pilot tone subset and the preset coefficients construct the equation, thereby eliminating crosstalk and accurately phase-detecting. The principle is explained below by taking m equal to 4 and n equal to 3.

, r ₂ , r ₃ , r ₄ ] = [yz ₀ ,

] , (z ₀ = e ^e ) When there is crosstalk, when the clock of the client and the office 60 is inconsistent, the model of the four consecutive DMT signals received by the UE is:

i , r ₂ , r ₃ , r ₄ ] = [yz, yz ² , yz ³ , yz ⁴ ] , (z = e' ^e ) where y is the signal received when the client and the central office 60 are clocked, z. The phase difference between the client and the central office 60 when there is no crosstalk. z is the phase difference between the client and the central office 60 when there is crosstalk, when z=z can be solved. , to eliminate crosstalk and achieve accurate phase discrimination.

For example, the central office 60 sends four DMT signals to the first user terminal, the second user terminal, and the third user terminal, respectively, and the first user terminal, the second user terminal, and the third embodiment in this embodiment. The coefficients of the pilot tone subset of the four DMT signals of the user end are not specifically limited, as long as the first user end and the second user end, the second user end and the third user end, and the first The user terminal ρ 23 and the coefficients of the pilot tone subsets of the four DMT signals of the third user end respectively constitute an orthogonal matrix. For example, the first user terminal, the second user terminal, and the third user terminal of the embodiment 4 The coefficients of the pilot tone subset of the DMT signals are: 1, -1, 1, and -1; 1, 1, -1, -1; 1, -1, -1, 1. In this embodiment, the preset coefficients are recorded as a1, a2, a3, and a4. It should be noted that, in this embodiment, the selection of the preset coefficient is not specifically limited, as long as the preset coefficient can be satisfied with the first user end. The coefficients of the pilot tone subsets of the four DMT signals of the second user end and the third user end respectively constitute an orthogonal matrix. For example, in this embodiment, al = l, a2 = l, a3 = 1, and a4 = 1, that is, the preset coefficients are 1, 1, 1, and 1.

Then, the coefficients and preset coefficients of the pilot tone subset of the four DMT signals of the three clients can be a\ a2 b 4 1 1 1 1

1 -1 1 -1 I - 1 1 -1

Form the orthogonal matrix W, for example, W is w

1 1 -1 -1 I I - 1 -1

1 -1 -1 1 1 -1 -1 1 The crosstalk model on the client side is F = F(H + Z), where Y is the signal received when the client and the central office 60 are in the same clock, and X is the central office 60. The transmitted signal; Z is the background noise, F is the frequency domain equalization coefficient, and H is the crosstalk coefficient. Since Z is much lower than the crosstalk noise, the Z is slightly excluded in this embodiment, and the crosstalk model before the UE side is FEQ (Frequency Domain Equalization) is F = H.

Illustratively, 1 of the above coefficients represents transmission X, and -1 represents transmission -x. Then, the four DMT signals sent by the central office 60 to the first user end are χ, -χ, χ, -χ;

When the client clock and the central office 60 clock are the same, the signals received by the three clients are respectively

H*W(2-A,:)x

] _{ +h + h _l3 -h +h _v

- ⁺

—h ₃ h _y where ^ , , respectively are the four signals continuously received by the first user end when the first user terminal clock and the central office 60 clock are consistent, respectively corresponding to the central office 60 transmitting to the first user end. 4 DMT signals χ, -χ, χ, -χ;

y _i ² , j ₂ ² , j ₃ ² , respectively, are four signals continuously received by the second user end when the second user terminal clock and the central office 60 clock are coincident, respectively corresponding to the central office 60 to the second user end 4 DMT signals sent χ, χ, -χ, -χ;

+ + +

y _i ³ , jj ₃ ³ , j ₄ ³ are respectively 4 signals continuously received by the third user end when the third user terminal clock and the central office 60 clock are consistent, respectively corresponding to the central office 60 sending to the third user end The four DMT signals are χ, -χ, -χ, χ.

Without loss of generality, the first user terminal is taken as an example for description. When the first user terminal clock and the central office 60 clock are inconsistent, the four signals Ar^A received by the first user end are: r{, r ₂ ,r ₃ ,r ₄ \ = \

|, where (1) is equivalently available:

Where _Z = e" ie: iiiiyyy A ^ where (1) utilizes the orthogonality of the w matrix

In particular, as can be seen from the above formula, (2:4,:)*, :))

therefore,

Al

A2

a\y _x + a2y ₂ + a3y ₃ + a4y ₄ [h, , ₂ h _l3 W{2: 4, :) * (W( :))' = 0 a3

A4

h _l3 W{2: 4, :) * (W( :))' = 0

Ie yl + y ₂ +yl +

( 2 ) Available from ( l ) ' and ( ² )

(3) Solve _ζ = ζ by equation (3). . Since the crosstalk signal has been eliminated in (2), the accuracy of the seek is greatly improved, thereby enabling the user to accurately detect the phase.

According to the above description, the signal sent by the central office 60 satisfies any two user terminals. When the coefficients of the pilot tone subset of the m DMT signals form an orthogonal matrix, the UE can construct an equation according to the coefficients of the pilot tone subset of the m DMT signals received by the UE and the preset coefficients, and solve the equation by solving the equation. Eliminates crosstalk for accurate phase discrimination.

twenty two"-'

W

twenty two"

1 1

1 -1 where k is a natural number greater than or equal to 1. For example, when n is equal to 3, m satisfies m>3, where = 2, and therefore 2 > Μ, the preferred k takes the smallest integer that satisfies the condition, thus = 2, m=4. The matrix ^ selected is:

1 1 1 1

I - 1 1 -1

Therefore ^

I I - 1 -1

1 -1 -1 1 For example, the central office 60 can send m DMT signals to the n user terminals according to any of the foregoing rules. This embodiment does not limit this. The following embodiment briefly describes a specific manner in which the central office 60 sends the DMT signal. rule.

For example, for the case of n UEs, the central office 60 transmits m DMT signals on the one or more pilot tones using any n rows other than the first row of the orthogonal matrix ^ according to the following rules, where A behavioral preset coefficient:

1. Align the DMT signals corresponding to the n lines;

2. Fixed constellation point X;

3. Number n clients, starting with 2, followed by 2, 3

4. The jth client sends the DMT signal according to the jth line, where 1 indicates that X is transmitted, and -1 indicates that -X is transmitted;

5. At the same DMT time, the central office 60 ensures that the same column of _m is sent.

A central office 60 is provided by the embodiment of the present invention. The central office 60 sends m DMT signals to each user end synchronously through n lines connected to n user terminals; one or more pilots are used for each line. The tone transmits m DMT signals; the corresponding n sets of one or more pilot tones on the n lines have at least one identical pilot tone subset; and the pilot tone subsets of the DMT signals are transmitted on any two lines The coefficients form an orthogonal matrix, so that the UE can obtain a signal consistent with the clock of the central office 60 according to the m DMT signals. The prior art has strong remote far-end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the UE is very low, thereby making the user terminal unable to accurately calibrate the clock.

FIG. 10 is a schematic diagram of another apparatus for the user terminal 70 according to an embodiment of the present invention. The user terminal 70 provided by the embodiment of the present invention can be applied to any Synchronous Time Division Duplexing (STDD), synchronous frequency. The DSL system of Synchronous Frequency Division Duplexing (SFDD) is described in this embodiment by taking the STDD system of Gfast as an example. Referring to FIG. 1, a schematic diagram of a Gfast system includes a central office, and the central office can connect n user terminals 70 through n lines connected to n client terminals 70, and each line can use one or more lines. Pilot tone Tone ) Sends a DMT signal.

As shown in FIG. 10, the client 70 can include:

The receiver 1001 is configured to receive m DMT signals sent by the central office, where the m DMT signals are sent by the central office to each of the user terminals 70 through n lines connected to the n user terminals 70; Transmitting, by each of the lines, the m DMT signals with one or more pilot tones; corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone a set; the coefficients on the pilot tone subset of the DMT signal on any two lines constitute an orthogonal matrix, the number 70 of the user end is greater than or equal to 2, the m is greater than the n; For example, the receiver 1001 may be further configured to: before receiving the m DMT signals sent by the central office, receive the indication information sent by the central office, where the indication information may include the pilot tone that the central office sends the DMT signal to the user end 70. The identifier information is used to receive the DMT signal sent by the central office according to the identification information of the pilot tone. The identifier information of the pilot tone may be the number information of the pilot tone or any other signal that can uniquely identify the pilot tone. information.

Exemplarily, the indication information may further include a preset coefficient, which may be determined in advance by the central office and the user end 70, or may be preset by the central office and then sent to the user end. This embodiment does not limit this.

Exemplarily, the preset coefficient is related to a coefficient of a pilot tone subset of the DMT signal sent by the central office to the UE 70, for example, a coefficient component on a pilot tone subset of the DMT signal transmitted on any two lines. In the orthogonal matrix, the number of clients n is greater than or equal to 2, and m is greater than n. The preset coefficients described above form an orthogonal matrix with the coefficients of the pilot tone subset corresponding to each line. The preset coefficients described above form an orthogonal matrix with the coefficients of the pilot tone subsets of the m DMT signals corresponding to each of the UEs 70. For example, the preset coefficients can be written as al, a2, a3, ..., am.

Correspondingly, the coefficients of the pilot tone subset of the m DMT signals corresponding to the n lines may constitute an orthogonal matrix of n*m, and the coefficients and preset coefficients of the m DMT signals corresponding to the n lines may constitute (n+ 1) An orthogonal matrix of *m.

Illustratively, m is the smallest natural number greater than n.

Exemplarily, the m DMT signals are transmitted by the central office to each of the user terminals 70 synchronously using n rows of the orthogonal matrix W on the n lines connected to the n user terminals 70, wherein the orthogonal matrix W The number of rows is greater than n, and the number of columns of the orthogonal matrix W is equal to m; Alternatively, the central office transmits m DMT signals to each of the user terminals 70 synchronously using any n columns of the orthogonal matrix W on the n lines connected to the n user terminals 70, wherein the columns of the orthogonal matrix W The number is greater than n, and the number of rows of the orthogonal matrix W is equal to m. Exemplarily, m = t , the orthogonal matrix W is a square matrix W _m of m order, and the recursive form of W _m is:

1 1

1 -1 where k is a natural number greater than or equal to 1.

The phase-locked loop 1002 is configured to obtain a signal consistent with the central office clock according to the m DMT signals received by each user terminal 70. For example, in order to obtain a signal consistent with the central office, the user terminal 70 needs to be consistent with the clock of the central office. For example, the user terminal 70 can track the clock of the central office through the phase locked loop 1002. Referring to FIG. 2, it is a phase lock. A schematic diagram of the structure of the ring 1002. The phase-locked loop 1002 includes a phase detector, a loop filter and a voltage controlled oscillator VCO. The signal received by the client 70 from the central office is used as an input signal of the phase detector. When the clocks of the terminals are inconsistent, the phase-locked loop outputs the phase difference between the user end 70 and the central office through precise phase discrimination, and then obtains a signal consistent with the central office through the loop filtering and the VCO.

According to the principle description in the method claim S503, when the signal transmitted by the central office satisfies the coefficients on the pilot tone subset of the DMT signal transmitted on any two lines to form an orthogonal matrix, the signal received by any user terminal 70 satisfies the arr. _lZ ^m - ¹ + a2r ₂ z ^m - ² + a3r ₃ z ^m - ³ + - - - + amr _m = 0 , therefore, the phase-locked loop 1002 can be based on the pilot tones of the m DMT signals received by the UE 70 The coefficients of the subset and the preset coefficients construct the equation, which can be solved by solving the equation; and the crosstalk is used for accurate phase discrimination. For example, the phase locked loop 1002 can construct an equation according to the coefficients of the pilot tone subset of the m DMT signals received by the UE 70 and the preset coefficients: alr _lZ ^m - ¹ + a2r ₂ z ^m - ² + a3r ₃ z ^m + · · · + amr _m = 0, thereby obtaining the phase difference between the client 70 and the central office.

For example, the client 70 can process the information received from the central office in accordance with the following rules to obtain an accurate phase difference: 1. The UE 70 starts receiving the DMT signal from any DMT signal including the above pilot tone;

2. The user terminal 70 sequentially records successive m DMT signals, which are recorded as rl, r2, r3, ..., r;

3. The user terminal 70 constructs an equation according to the received m DMT signals and the preset coefficients sent by the central office. For example, when the preset coefficients sent by the central office are al, a2, a3, and am, the equation constructed by the user end is: a\rz ^m ' + a2r ₂ z ^m - ² + a3r ₃ z ^m - ³ +■■■ + amr _m = 0;

5. The client 70 uses S as the output of the phase detector.

6. The clock of the user terminal 70 is calibrated according to the phase-locked loop 1002; m DMT signals are obtained consistent with the central office clock; for example, the user terminal 70 can periodically repeat the rules 2 to 6 of the above rule, thereby A continuous signal consistent with the central office clock can be obtained.

It should be noted that when there are a large number of client terminals 70 connected by the authority, the central office can group the client terminals 70, and the central office sends the DMT signals to each group by using the above method, so that the user terminals 70 in each group can respectively Perform accurate clock recovery to obtain a signal consistent with the central office.

The user terminal 70 is provided by the embodiment of the present invention. Each user terminal 70 receives m DMT signals sent by the central office, and the m DMT signals are synchronously transmitted by the central office through n lines connected to the n user terminals 70. A user terminal 70 transmits; each line uses one or more pilot tones to transmit m DMT signals; and corresponding n groups of one or more pilot tones on the n lines have at least one identical pilot tone subset And the coefficients on the pilot tone subset of the DMT signal transmitted on any two lines form an orthogonal matrix, and the UE 70 can perform accurate clock calibration according to the received m DMT signals to obtain a signal consistent with the central office clock. . The prior art has strong remote far-end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the UE 70 is very low, thereby making the user terminal 70 unable to accurately calibrate the clock.

On the other hand, an embodiment of the present invention provides a system for clock recovery, including the central office 60 described in any of the foregoing embodiments, and the user terminal 70 described in any of the foregoing embodiments. In the clock recovery system provided by the embodiment of the present invention, the central office 60 transmits m DMT signals to each user terminal 70 synchronously through n lines connected to the n user terminals 70; one or more lines are used for each line. One pilot tone transmits m DMT signals; corresponding on n lines The n sets of one or more pilot tones have at least one identical pilot tone subset; and the coefficients on the pilot tone subset of the DMT signal transmitted on any two lines form an orthogonal matrix, so that the user terminal 70 can m DMT signals acquire signals consistent with the central office 60 clock. The prior art has strong remote end interference due to spectrum spreading, so that the SNR of the clock synchronization pilot signal received by the user terminal 70 is very low, thereby making the user terminal 70 unable to accurately calibrate the clock.

A person skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working process of the system, the device and the unit described above can be referred to the corresponding process in the foregoing method embodiment, and details are not described herein again.

In the several embodiments provided herein, it should be understood that the disclosed systems, apparatus, and methods may be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the unit is only a logical function division. In actual implementation, there may be another division manner, for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored, or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.

The units described as separate components may or may not be physically separate. The components displayed as units may or may not be physical units, i.e., may be located in one place, or may be distributed over multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solution of the embodiment.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may be physically included separately, or two or more units may be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of hardware plus software functional units.

The above-described integrated unit implemented in the form of a software functional unit can be stored in a computer readable storage medium. The software functional unit described above is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, server, or network device, etc.) to perform portions of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like, which can store program codes. Medium. It should be noted that the above embodiments are only for explaining the technical solutions of the present invention, and are not intended to be limiting; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that: The technical solutions described in the foregoing embodiments are modified, or some of the technical features are equivalently replaced. The modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. It should be covered by the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the appended claims.

Claims

Claim

A method for clock recovery, the method comprising:

The central office connected to the n user terminals respectively generates m DMT signals for each user terminal; the central office sends m DMT signals to each user terminal synchronously through n lines connected to the n user terminals. Wherein each of the lines transmits the m DMT signals with one or more pilot tones; the corresponding n groups of the one or more pilot tones on the n lines have at least one identical pilot a subset of the pilot tone subsets on which the DMT signals are transmitted on any two lines constitute an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n ;

The m DMT signals of the user end are used by the UE that receives the m DMT signals to obtain a signal consistent with the central office clock according to the m DMT signals.

2. The method of clock recovery according to claim 1, wherein before the central office transmits m DMT signals to each of the UEs synchronously through n lines connected to the n user terminals, The method further includes:

The office sends the indication information to each user end, where the indication information includes identifier information of the pilot tone subset of the DMT signal and a preset coefficient, and the preset coefficient is sent on each line. The coefficients on the set of pilot tones of the DMT signal form an orthogonal matrix.

3. A method of clock recovery according to claim 1 or 2, wherein said m is a minimum natural number greater than said n.

The method for clock recovery according to any one of claims 1 to 3, wherein the central office sends m to each user terminal synchronously through n lines connected to the n user terminals. DMT signals, including:

The central office sends m DMT signals to each user end synchronously using any n rows of the orthogonal matrix W on the n lines connected to the n user terminals, where the orthogonal matrix W The number of rows is greater than n, and the number of columns of the orthogonal matrix W is equal to m;

Or,

5. The method of clock recovery according to claim 4, wherein said = ² , The orthogonal matrix W is a square matrix W m of the order _m , and the recursive form of the \¥„ ₁ is

^―' w _2l .

W

-w

1 1

1 -1 where k is a natural number greater than or equal to 1.

A method for clock recovery, the method comprising:

Each of the UEs receives m DMT signals sent by the central office, and the m DMT signals are sent by the central office to each user end through n lines connected to the n user terminals; wherein, each line Transmitting, by the one or more pilot tones, the m DMT signals; the corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone subset; Transmitting the coefficients on the pilot tone subset of the DMT signal on two lines to form an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n; Obtaining a signal consistent with the central office clock according to the received m DMT signals.

The method for recovering a clock according to claim 6, wherein before the receiving, by each client, the m DMT signals sent by the central office, the method further includes:

Each user terminal receives the indication information sent by the central office, where the indication information includes identifier information of the pilot tone subset of the DMT signal and a preset coefficient, where the preset coefficient is on each line. The coefficients on the set of pilot tones that transmit the DMT signal form an orthogonal matrix.

8. A method of clock recovery according to claim 6 or 7, wherein said m is a minimum natural number greater than said n.

The clock recovery method according to any one of claims 6-8, wherein the m DMT signals are respectively used by the central office on n lines connected to the n user terminals. Any n rows of the orthogonal matrix W are synchronously transmitted to each of the user terminals, wherein the number of rows of the orthogonal matrix W is greater than n, and the number of columns of the orthogonal matrix W is equal to m;

10. The method of clock recovery according to claim 9, wherein said = ² , The orthogonal matrix W is a square matrix W m of the order _m , and the recursive form of the \¥„ ₁ is

^―' w _2l .

W

-w

1 1

1 -1 where k is a natural number greater than or equal to 1.

The clock recovery method according to any one of claims 7 to 10, wherein each of the user terminals obtains the same as the central office clock according to the received m DMT signals. Signals, including:

Each user end acquires a phase difference between each user end and the central office according to the received m DMT signals and the preset coefficient;

Each client performs clock calibration based on the phase difference to obtain a signal consistent with the central office clock.

12. A central office, characterized in that:

a processor, configured to generate m DMT signals for each of the n clients connected to the central office;

a transmitter, configured to send, by using n lines connected to the n terminals, m DMT signals to each user end; wherein each line transmits the m pieces by using one or more pilot tones a DMT signal; a corresponding n sets of the one or more pilot tones on the n lines having at least one identical pilot tone subset; wherein the pilots of the DMT signal are transmitted on any two of the lines The coefficients on the subset of the sound constitute an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n;

13. The central office according to claim 12, wherein

The transmitter is further configured to: send, to each user end, indication information, before the sending, by the n lines connected to the n user terminals, the m DMT signals to each user end, where the indication information includes Transmitting identification information of the pilot tone subset of the DMT signal and a preset coefficient, where the preset coefficient is orthogonal to a coefficient on the pilot tone subset of the DMT signal sent on each line matrix.

14. The central office according to claim 12 or 13, characterized in that The m is a minimum natural number greater than the n.

The central office according to any one of claims 12 to 14, wherein the transmitter is further configured to: use an arbitrary matrix W on each of the n lines connected to the n user terminals. n rows synchronously send m DMT signals to each client, wherein the number of rows of the orthogonal matrix W is greater than n, the number of columns of the orthogonal matrix W is equal to m;

Or for transmitting, on each of the n lines connected to the n user terminals, m DMT signals to each of the UEs using any n columns of the orthogonal matrix W, wherein the orthogonal matrix W The number of columns is greater than n, and the number of rows of the orthogonal matrix W is equal to m.

16. The central office according to claim 15, wherein:

The = ² , the orthogonal matrix W is a square matrix W m of the order _m , and the recursive form of the W „^々 is:

1 1

1 -1 where k is a natural number greater than or equal to 1.

17. A client, characterized in that:

a receiver, configured to receive m DMT signals sent by the central office, where the m DMT signals are sent by the central office to each user end through n lines connected to the n user terminals; wherein, each of the The line 发送 transmitting the m DMT signals with one or more pilot tones; the corresponding n sets of the one or more pilot tones on the n lines have at least one identical pilot tone subset; The coefficients on the pilot tone subset of the DMT signal transmitted on any two lines form an orthogonal matrix, the number n of the user terminals is greater than or equal to 2, and the m is greater than the n; the phase locked loop, And acquiring, according to the m DMT signals received by the receiver, a signal consistent with the central office clock.

18. The client according to claim 17, wherein:

The receiver is further configured to: before receiving the m DMT signals sent by the central office, receive the indication information sent by the central office, where the indication information includes an identifier of the pilot tone subset that sends the DMT signal The information and the preset coefficient, the preset coefficient and the coefficient on the pilot tone subset of the DMT signal transmitted on each line form an orthogonal matrix.

19. The client according to claim 17 or 18, characterized in that The m is a minimum natural number greater than the n.

The user terminal according to any one of claims 17 to 19, wherein the m DMT signals are orthogonally used by the central office on n lines connected to the n user terminals respectively. Any n rows of the matrix W are synchronously transmitted to each of the user terminals, wherein the number of rows of the orthogonal matrix W is greater than n, and the number of columns of the orthogonal matrix W is equal to m;

21. The client according to claim 20, wherein:

twenty two"

W

twenty two"

1 1

1 -1 where k is a natural number greater than or equal to 1.

The user terminal according to any one of claims 17 to 21, wherein the phase locked loop is further configured to:

Obtaining a phase difference between each user end and the central office according to the m DMT signals received by each user terminal and the preset coefficient;

Performing clock calibration according to the phase difference to acquire a signal consistent with the central office clock.

A system for clock recovery, comprising the central office according to any one of claims 12-16 and the user terminal according to any one of claims 17-22.